1. Maybe you've missed some lines with Lae'zel. She doesn't mention any names, but she's bragging about her experience in bad and how good she is etc etc
2. While Gale may not be the one that had many partners before, his persistence is well known, even acknowledged by Larian themselves and they even tried to patch it already. You must be blind to don't see what even developers saw.
3. Exactly, she is completely inexperienced about normal relationships, yet totally sexually traumatized. Have you missed some lines again? Her memories were wiped again and again so she would willingly have sex with yet another partner.
4. Yes.
5. Yes.
6. This one is the only one I am not sure about. Still from what Mizora tells us and from his reaction to our romance with her we can be almost sure he was forced into sex with her.
So, all in all, the only diversity we have there is a diversity of sex trauma and/or perverseness. Weird writing to say the least.
Maybe I did miss those Lae'zel lines. I remember her bragging about how skilled she was, but maybe I wrote that off as her usual braggadacio about everything, not necessarily that she was actually experienced or anything.
However, I dispute your claim about Gale. What the devs patched was not his persistence, what they patched was giving you another option in the initial flirting encounter that was somewhere between "reciprocate his flirting" and "reject him as harshly as possible." It could be that Gale seems persistent because a lot of people who wanted to reject him didn't choose the harshest rejection lines.
But like, your broader claim that all there is is perversion and sex trauma just doesn't seem true. Lae'zel, well she's a weird one, by her culture's standards she's likely not perverse at all. Gale seems neither perverse (even with his perhaps somewhat unintended persistence) or sexually traumatized. Shadowheart is traumatized in general, though it seems that the 'casual' attitude towards sex is really just the teachings of Shar in general. Like, without the messed up specifics of her situation, if she had just been a normal follower of Shar, it seems like she might have ended up with the same attitude toward sex. Astarion is, well, Astarion. Karlach....I guess it depends on your definition of "perverse." To me it means a bit more than simply "enjoys sex". Again, she's a weird one, because she's in a situation in the game (having not been able to touch people for years) where it is understandable that she's a little 'pent up' and eager to get back into business. It's arguable, but I guess she never came across to me as "perverse". Wyll, I just don't know, he's just so boring to me I ignore him all the time.
I think maybe this is the problem of having a limited number of companions and having a policy that you could romance any of them. Within a game that is, actually, relatively narratively short, that means that (especially towards the beginning of the game, where it's going to be trying to trigger the romances) it's going to seem like ALL your companions are flirting with you all the time. BG2, on the other hand, had multiple companions you COULD romance, but the overwhelming majority of them were actually not interested in romance at all. I don't mind the romances that exist in BG3...but I do think that compared to the previous games there's a real shortage of companions to choose from in general, and if they were going to add more they could make them all non-romantic options.
